text stringlengths 1 1.11k | source dict |
|---|---|
\eqalignno{ S & = \left \{\left .\left [\array{ {x}_{1} \cr {x}_{2} \cr {x}_{3} \cr {x}_{4} } \right ]\right \vert {x}_{1} = −3{x}_{3} + 2{x}_{4},\kern 1.95872pt {x}_{2} = −{x}_{3} + 3{x}_{4}\right \} & & \cr & = \left \{\left .\left [\array{ −3{x}_{3} + 2{x}_{4} \cr −{x}_{3} + 3{x}_{4} \cr {x}_{3} \cr {x}_{4} } \right ]\right \vert {x}_{3},\kern 1.95872pt {x}_{4} ∈ {ℂ}^{}\right \} & & \cr & & }
After working through these examples, you might perform the same computations for the slightly larger example, Archetype J. | {
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"openwebmath_perplexity": 1463.3392804900752,
"openwebmath_score": 0.9845515489578247,
"tags": null,
"url": "http://linear.ups.edu/jsmath/0230/fcla-jsmath-2.30li20.html"
} |
java, thread-safety, matrix
@Test
public void testEquals_NullElements_SameTemplateParameters() {
assertEquals(matrix, new MatrixNotThreadSafe<Integer>(ROWS, COLUMNS));
}
@Test
public void testEquals_DifferentDimensions_NullElements() {
Matrix<Integer> matrix1 = new MatrixNotThreadSafe<Integer>(2, 2);
Matrix<Integer> matrix2 = new MatrixNotThreadSafe<Integer>(2, 1);
assertFalse(matrix1.equals(matrix2));
}
@Test
public void testEquals_NotNullElements_With_NullElements() {
Matrix<Boolean> falseElements = getMatrixInitializedByFalse(ROWS, COLUMNS);
Matrix<Boolean> nullElements = new MatrixNotThreadSafe<Boolean>(ROWS, COLUMNS);
assertFalse(falseElements.equals(nullElements));
}
@Test
public void testHashCode_NotThrowsExceptions() {
matrix.hashCode();
}
} Position | {
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"tags": "java, thread-safety, matrix",
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Since this notation is cumbersome, let ${A=\Gamma(X, \mathcal{C})}$ and ${\bigwedge^*=\bigwedge^*\overline{T}}$.
Let ${i: \bigwedge \rightarrow A\otimes_\mathbb{C} \bigwedge}$ be the inclusion. We want to show this gives an iso ${\bigwedge^q\stackrel{\sim}{\rightarrow} H^q(X, A\otimes \bigwedge^*)}$. This is precisely the goal given at the start of the post. | {
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"lm_q2_score": 0.8615382076534743,
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"openwebmath_score": 0.9643252491950989,
"tags": null,
"url": "https://hilbertthm90.wordpress.com/category/math/manifolds/page/2/"
} |
human-biology, cell-biology, neuroscience, neurophysiology, pain
The last type of pain, which is the sympathetic pain falls into, is called neuropathic pain. This pain is more abstract and is often described as constant and idiosyncratic (non standard intervals). In research it is often modeled by inducing diabetes and doing damage to the nerves to cause constant pain signals to the brain. However, the method is controversial in both practice and in efficiency of modeling. This because there are often many different biological ways to induce cognitive pain and it is primarily central nervous system based (aka in the brain), whereas this type of pain is specifically induced by nerve damage (hence neuropathic). This type of pain is often tested using cognitive based test parameters to see if a drug can relieve some of the mental struggles either caused by the pain or causing the pain. There are also such cells called "mirror neurons" that fire when you sense (visual, audio, touch) something and then cause a similar behavior or sensation to occur | {
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"tags": "human-biology, cell-biology, neuroscience, neurophysiology, pain",
"url": null
} |
machine-learning, reinforcement-learning, alphago, alphazero, alphago-zero
How is the network trained to understand that if all it is told is who eventually won?
To my understanding, this is basically a supervised learning problem, where from the self play we have games associated with their winners, and the network is being trained to map game states to likelihood of winning. | {
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"url": null
} |
algorithm, graph, f#
131 14,358 98,4614 159,4355 75,5902 22,6075 43,8231 163,8625 11,833 57,6342 61,6924 82,3457 64,4631 134,6293 167,6269 2,7005 63,5257 9,700 103,2920 21,3748
132 198,2393 113,5383 99,6234 138,5667 28,5604 19,3157 38,6092 85,3873 82,4162 25,219 182,6433 22,1560 147,2847 6,1514 121,3867 128,2789 51,6107 37,821
133 80,7217 112,9083 136,3739 77,2481 39,8145 43,8488 18,2702 27,7749 168,899 99,2090 190,9958 139,4719 182,8241 191,4296 85,836 153,8437 67,3802 49,5167 111,6767
134 197,6225 198,4071 92,610 79,5792 175,4489 36,979 131,6293 71,7485 146,9556 158,119 11,294 65,9956 135,276 16,5203 84,9312 126,5002 38,4730
135 23,4560 4,7582 20,6434 174,6977 150,9732 190,1431 173,5664 144,6396 127,1752 122,6345 48,8869 82,519 158,8348 184,7629 78,6919 10,4650 134,276 194,5726 13,861 | {
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} |
fluid-dynamics, waves, acoustics, lightning, meteorology
Finally, concerning cloud formation: this also is a big issue in many parts of the world so one would think that if bells could help then it would have been noticed and documented more fully and convincingly by now. Disturbing air which is already supersaturated will in general encourage (not discourage) droplets to form. However there have been many efforts to do this by seeding the air and it appears that it is hard to do on a large enough scale to have any useful impact. | {
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"tags": "fluid-dynamics, waves, acoustics, lightning, meteorology",
"url": null
} |
c#, tic-tac-toe
{
bool Control = false;
for (int j = 0; j < this.Matrix.GetLength(0); j++)
{
Array.Clear(Vector, 0, Vector.Length);
for (int i = 0; i < this.Matrix.GetLength(1); i++)
{
this.Vector[i] = this.Matrix[i, j];
}
if (!ArrayValidator.HasBlank(this.Vector))
Control = ArrayValidator.HasSameValues(this.Vector);
}
return Control;
}
private bool MainDiagonalValidator()
{
bool Control = false;
Array.Clear(Vector, 0, Vector.Length);
for (int i = 0; i < this.Matrix.GetLength(0); i++)
{
for (int j = 0; j < this.Matrix.GetLength(1); j++)
{
if (i == j)
this.Vector[j] = this.Matrix[i, j];
}
}
if (!ArrayValidator.HasBlank(this.Vector)) | {
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"tags": "c#, tic-tac-toe",
"url": null
} |
operating-systems, memory-hardware, filesystems
Title: Deleted data remains on a disk until? I am little bit confused between the two answers below.
What is the exact answer of this question?
My query is,
"Deleted data remains on a disk until...?"
The data is overwritten;
The recycle bin is emptied.
I have searched it over internet and books, but I have found various answers.
Please explain to me.
Thank you in advance. It depends on the file system used and preferences provided, but in the most common case - deleted data is marked as deleted (dirty) and is used when some new data is to be written. Priority of usage of dirty block earlier than empty depends on system preferences.
The recycle bin is different case - until emptied there is guarantee to recover files, so it is not deleted per se.
After recycle bin is emptied file is deleted (so flagged as deleted and then based on preferences stays there or is physically deleted). | {
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"tags": "operating-systems, memory-hardware, filesystems",
"url": null
} |
python, performance, numpy, statistics
#CAL
ES_POWER_X_WT_A = pow(ZVAL_A,2) * WT_A #float
ES_POWER_X_WT_B = pow(ZVAL_B,2) * WT_B #float
WT_POWER_A = pow(WT_A,2)
WT_POWER_B = pow(WT_B,2)
SumofES_POWER_X_WT = ES_POWER_X_WT_A + ES_POWER_X_WT_B
SumofWT_POWER = WT_POWER_A + WT_POWER_B
#COMPUTE TAU
tmp_A = ZVAL_A - meanES
tmp_B = ZVAL_B - meanES
temp = pow(SumofZVAL_X_WT,2)
Q = SumofES_POWER_X_WT - (temp /(SumofWT))
if PCC_A !=0 or PCC_B !=0:
df = 0
else:
df = 1
c = SumofWT - ((pow(SumofWT,2))/SumofWT)
if c == 0:
tau_square = 0
else:
tau_square = (Q - df) / c
#calculation
Var_total_A = Var_A + tau_square
Var_total_B = Var_B + tau_square
WT_total_A = float(1) / Var_total_A
WT_total_B = float(1) / Var_total_B
ZVAL_X_WT_total_A = ZVAL_A * WT_total_A
ZVAL_X_WT_total_B = ZVAL_B * WT_total_B
Sumoftotal_WT = WT_total_A + WT_total_B
Sumoftotal_ZVAL_X_WT= ZVAL_X_WT_total_A + ZVAL_X_WT_total_B | {
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And, after the fifth toss......the probabilty is just....1 - (1/2)^1 = 1/2 = .50 ......just what we would expect it to be on one remaining toss !!!
This demonsrates something known as the Gambler's Fallacy......(it's why those big buildings exist in Las Vegas....!!!).......why does this happen???....because, as more "failures" pile up in the sequence of some N trials, the fewer chances there are remaining for a person to achieve a success........!!!
CPhill Dec 9, 2014
Sort:
#1
+92193
+5
$$\frac{1}{2^6}=\frac{1}{64}$$
Melody Dec 9, 2014
#2
+85624
+5
There's something interesting about this problem that I'd like to bring out.....many people think that there is some "righting" force in nature that tends to bring things "back to center"....in this case........many think that, if they haven't been successful after "N" flips, that there is a greater chance that they WILL be successful on the next flip......this isn't true as shown below... | {
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"tags": null,
"url": "https://web2.0calc.com/questions/what-are-the-odds-of-losing-6-coin-flips-in-a-row"
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The two notions are the same (up to isomorphism) for vector spaces whose intersection is $\{0\}$. Assume $U$ and $V$ are vector spaces such that $U \cap V = \{0\}$. I'll refer to their external direct sum $(1)$ as $U\times V$ and their internal direct sum $(2)$ as $U \oplus V$.
As mentioned in the comments $U \times V \cong U \oplus V$, and the isomorphism is the natural choice. The only thing that requires a bit of thinking is noticing where the condition $U\cap V = \{0\}$ comes in. The isomorphism is the following:
\begin{align} \phi : U \times V &\to U \oplus V \\ (u,v) &\mapsto u + v \end{align} | {
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"url": "https://math.stackexchange.com/questions/2491318/there-appears-to-be-two-definitions-of-the-direct-sum-of-vector-spaces"
} |
java, beginner, array
Title: Finding the largest value in a 2D array I'm pretty new to Java and programming in general and I'm doing practice problems from my textbook over the summer to try to get ahead. This is a simple program that finds the largest value in a 2D array. I'm just looking for feedback on the organization of my code as well as any improvements I can make so that I can build solid habits going forward.
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("Enter the number of rows and columns in the array: ");
//Creates a temporary two-dimensional array whose size is the next two inputed integers
double[][] temp = new double[input.nextInt()][input.nextInt()]; | {
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impossible that there could be some implication of this kind, as the argument you gave for the $2\times2$ case illustrates, but deducing equalities from inequalities is not an obvious kind of thing in algebra. This could lead you to suspect the extra condition was not the proper way to rule out the counterexample, and being able to resuscitate it is the simplest way to be sure it is not. | {
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"openwebmath_perplexity": 186.27573543601332,
"openwebmath_score": 0.8965259194374084,
"tags": null,
"url": "http://bootmath.com/is-the-square-root-of-a-triangular-matrix-necessarily-triangular.html"
} |
python, python-3.x, csv
def buildFieldNameDict(csvListData, fieldNames):
result = []
for line in csvListData:
result.append(dict([(name, value) for name, value in zip(fieldNames, line)]))
return result
csvListData = parseCSVData(myCSVString)
csvFieldDataDict = buildFieldNameDict(csvListData, ['Name', 'Fav_num', 'Birth_month', 'Birth_date', 'Birth_year'])
Overall I would not try to reinvent the wheel if Python provides what you need since it's already written and maintained for you. But this can be a good learning exercise. | {
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• $f'(x_m) = 0$ or $x_m$ is a remarquable point (here $x_m \in \{-3,-1,2\}$)
• $f'$ changes sign before and after $x_m$
If the second condition is not verified, $x_m$ is an inflection point.
• I think x=0 is another remarkable point here, since f'(x) becomes undefined at x=0 . – MathsLearner Jun 6 '17 at 15:30
• You're absolutely right, I didn't do the $f'$ study before posting my answer but indeed as pointed out by Dando18 if $f'$ is undefined then you should check the nature of the point. – Furrane Jun 8 '17 at 2:38 | {
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"openwebmath_score": 0.8031412959098816,
"tags": null,
"url": "https://math.stackexchange.com/questions/2312085/counting-total-number-of-local-maxima-and-minima-of-a-function"
} |
ros, bashrc, qt4
But when I run cmake in qtCreator, I get the following error:
CMake Error at /opt/ros/indigo/share/catkin/cmake/safe_execute_process.cmake:11 (message):
execute_process(/usr/bin/python
"/home/sharath/catkin_ws/build/catkin_generated/generate_cached_setup.py")
returned error code 1
Call Stack (most recent call first):
/opt/ros/indigo/share/catkin/cmake/all.cmake:186 (safe_execute_process)
/opt/ros/indigo/share/catkin/cmake/catkinConfig.cmake:20 (include)
CMakeLists.txt:52 (find_package)
File "/home/sharath/catkin_ws/build/catkin_generated/generate_cached_setup.py", line 20, in <module>
from catkin.environment_cache import generate_environment_script
ImportError: No module named catkin.environment_cache
Traceback (most recent call last):
-- Using CATKIN_DEVEL_PREFIX: /home/sharath/catkin_ws/devel
-- Using CMAKE_PREFIX_PATH:
-- Using PYTHON_EXECUTABLE: /usr/bin/python
-- Using Debian Python package layout
-- Using empy: /usr/bin/empy
-- Using CATKIN_ENABLE_TESTING: ON | {
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"tags": "ros, bashrc, qt4",
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recurrence-relation
More generally, there are no rules on how to solve recurrence relations (or anything in mathematics). Having seen the Master theorem, you know what to do when you have a recurrence of the form $S(n) = \alpha S(n/\beta) + f(n)$. Having seen this example, you know (a) what to do when you have a recurrence $T(n) = \alpha T(n^\beta) + f(n)$, and (b) it is a good idea to try to reduce a general recurrence to one of the form $S(n) = \alpha S(n/\beta) + f(n)$ by using an appropriate substitution.
As you get deeper into the subject (if you choose to do so), you will learn more tricks that will help you solve problems. Yet sometimes a new trick will be necessary. When all else fails, you just try a lot of things with your recurrence. Hopefully, after a while a winning direction will emerge. This is called (mathematical) research. | {
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"tags": "recurrence-relation",
"url": null
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object-oriented, ruby, chess
##
# Returns an array of coordinates that can be reached by recursively
# applying the given +move+, starting from the +from+ coordinates
private
def repeated_move(from, move, valid_moves = [])
coords = relative_coords(from, move)
return valid_moves unless possible_move?(coords)
return valid_moves << coords unless @board.at(coords).nil?
repeated_move(coords, move, valid_moves << coords)
end
##
# Returns coordinates that will be reached after applying the +move+,
# starting from the +from+ coordinates
def relative_coords(from, move)
[from[0] + move[0], from[1] + move[1]]
end
##
# Returns true if:
# * The 8x8 board exists at given coordinates
# * Board at given coordinates is empty or it contains a piece with the same
# color as the current_color | {
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"tags": "object-oriented, ruby, chess",
"url": null
} |
newtonian-mechanics, classical-mechanics, angular-momentum, rotational-dynamics
Thus by definition angular momentum as the moment of momentum (linear momentum at a distance) we derive the equations of motion at the center of mass
$$\left. \begin{aligned}
\boldsymbol{p} & = m\, \boldsymbol{v}_C \\
\boldsymbol{L}_C & = \mathrm{I}_C \boldsymbol{\omega}
\end{aligned}\, \right\} \begin{aligned}
\boldsymbol{F}_{\rm net} & = \frac{\rm d}{{\rm d}t} \boldsymbol{p} = m\, \boldsymbol{a}_C \\
\boldsymbol{\tau}_{\rm net} & = \frac{\rm d}{{\rm d}t} \boldsymbol{L}_C = \mathrm{I}_C \boldsymbol{\alpha} + \boldsymbol{\omega} \times \boldsymbol{L}_C
\end{aligned} $$ | {
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} |
Initial Points at The Origin. If you walk straight along the path, your direction can be considered a unit vector and its magnitude is 1. The basic idea behind vector components is any vector can be composed (put together) from component vectors. Unit vectors are typically introduced as “sign posts”, e.g., the unitvectors North, South, West ,andEast shown to the right. vector-unit-calculator. #color(blue)(|OA| = sqrt(3^2+3^2)# #rArr sqrt(18)# units. The magnitude of v follows the formula. We have. A unit normal vector of a curve, by its definition, is perpendicular to the curve at given point. 9. Isotropic vector or null vector, in a vector space with a quadratic form, a non-zero vector for which the form is zero. You will need this skill for computing flux in three dimensions. (We define the cross product only in three dimensions. Linearly Dependent Vectors. This means a normal vector of a curve at a given point is perpendicular to the tangent vector at the same point. If you chose v1 | {
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"lm_q1_score": 0.9518632247867715,
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"tags": null,
"url": "http://botan.es/5bacvvfu/unit-vector-formula-580664"
} |
forces, torque, rotation, space
Note: Assume the rod is initially at rest in space and the frame of reference is a stationary observer. The second question there (yours) isn't about a situation where there is "pure torque".
You only have one force acting on the object, so it creates a torque and moves the centre of mass because there is a net force. A "pure torque" requires a "force couple" where the two forces cancel out on the centre of mass as $0$ net force; but due to the direction of the forces, it still produces a net torque on the object, which causes rotation without translation (A.K.A. pure torque, pure moment, or pure rotation).
Another interesting thing about a pure torque is that the moment is independent on the point you are measuring torque about; which is a special feature of pure torque. If you apply a pure torque, the moment vector at one end would be the same as the moment vector of the centre of mass, which is an interesting result not typical of non-pure moments. | {
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quantum-mechanics, quantum-field-theory, special-relativity, photons, wavefunction
What I don't get is why? Why does being massless mean a particle can't be localized? This answer to a related question says it's because photons don't preserve causality because they can go back in time, which doesn't make any sense to me -- isn't SR supposed to preserve causality? And even if it didn't, what does that have to do with position? I will only make an answer about the position operator.
The most well-defined things that we may reliably say that we can measure, are Hamiltonian eigenvalues. It should be good on hindsight---you can keep measuring in succession, over a region of time, and keep getting the same value. This is the most certain we may become of anything in quantum theory. | {
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c#, optimization, unity3d
Title: Is there a beter way to check input besides a switch case? So I am running a Switch case to check if a user has filled in all the necessary fields within a form, and if not I prompt them to do so. I was wondering if there was a better way to do this, or if a switch case like this would suffice. General suggestions/naming improvements would also be appreciated.
This runs inside the unity engine, on unity C#
void CheckEmptyValues()
{
/* Step wise checks certain Necessary values, if things are not assigned it breaks the operation
* And prompts the user to fill in the appropriate slot
*/
int caseSwitch = 0;
switch (caseSwitch)
{
case 0:
if (GalleryName == null || GalleryName == "Default")
{
Debug.Log("No Gallery name assigned, please give the gallery a proper name");
break;
}
else goto case 1;
case 1:
//This is a rectangle | {
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newtonian-mechanics, forces, rotational-dynamics, torque
Title: Do internal forces always act along the line joining the particles? For the rate of change of angular momentum of a system to be equal to the torque due to external forces, the torque due to internal forces should be zero. This will mathematically be possible only when the internal forces act along the line joining the particles.
Is this condition valid in all the cases? If not kindly explain with examples. The forces between pairs of magnetic dipoles are not central, and in general neither are the chemical bonding forces that hold things together.
That central forces imply that angular momentum is conserved is true. The converse, that angular momentum conservation implies central forces, is not true. | {
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java, beginner
/* If ordered and has arrived */
} else if (orderInTravel && orderTravelTime >= item_1.getLeadTime()) {
orderTravelTime = 0;
orderInTravel = false;
quantityIn += item_1.getReOrder();
out += "New Stock Delivered (" + item_1.getReOrder()") and Will be Added to Quantity in Stock the Next Day";
}
/* If stock gets too low, order */
if (quantityIn < reOrderThreshold) {
orderInTravel = true;
out += "Ordered";
}
/* Print out results */
System.out.println(out);
}
Here is part of the output:
Day Stock Order Status | {
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php, pdo
that $valuearray
the way empty() is used. In fact, to get 1 or 0 from a boolean value you can simply cast it as int
So what could we have after all these improvements?
First of all, separate the data validation from the query execution.
Validate all the data first,
$errors = [];
// perform all other validations
foreach($array2 as $value) {
if ((isset($value['coord']) || isset($value['bookedbefore'])) && isset($value['bookedslot'])) {
$errors[] = "Error: you ticked checkbox(es) on the booking selection setting without choosing a corresponding slot";
break;
}
} | {
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The solution in the book used projections and I understand why it worked (the answer is 2), but I can't find what went wrong in my solution. Thanks for helping.
2. Sep 17, 2012
### chiro
Hey MartinBob and welcome to the forums.
The first thing to do is to normalize your plane equation.
You have x + 2y + 2z = 6 or x + 2y + 2z - 6 = 0 or ax + by + cz + d = 0.
Now <a,b,c> constitute a vector perpendicular to the plane: we want to normalize this vector and adjust the rest of the equation.
So normalize <1,2,2> gives a length of SQRT(1^2 + 2^2 + 2^2) = SQRT(9) = 3. So by normalizing the vector we must divide our whole equation by 3 and this gives us:
(1/3)x + (2/3)y + (2/3)z + 2 = 0.
Now in normalized form if we want to find the distance from any point to the plane, we can use the fact that (2-d) = <1/3,2/3,2/3> . p where . is the dot product and p is a point. | {
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python, beginner, python-3.x, file-system
if __name__ == "__main__":
main()
I believe that my logic is closer to a functional programming style
It isn't, and new developers often confuse this with procedural programming; yours is the latter.
Otherwise:
Avoid os and shutil when Path has the same functionality with more convenient representation
This application does not need regular expressions. Globs are more rudimentary, but fit the job. Internally they use regular expressions anyway, but it's still probably a good idea to use the more constrained interface.
I don't think that you should exclude prefixes that have no numbers. And I think that your definition of prefix is a little odd. The word "spam" alone should be your prefix.
check_user_input should not return string-or-bool; it should throw-or-not.
create_file_list would be well-represented by a generator function.
You can replace listdir with glob.
Consider separating your gap identification code from your renaming code. | {
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javascript, array
Because basically I have to group the child arrays by whatever is in their second index, or [1], and then join them with " or ".
I am successful but I'm afraid this isn't really the best way to acheive this. Isn't there a more simple way to do this?
var
filters = [["Apples", "fruitgroup", "123"], ["Bananas", "fruitgroup", "012"], ["Jumbo Jet", "planegroup", "99"], ["Crop duster", "planegroup", "40"], ["Melons", "fruitgroup", "55"]],
fieldnames = _.uniq(_.map(filters, function (filter) {
return filter[1];
})),
groups = _.groupBy(filters, function (filter) {
return filter[1];
}),
strings = _.map(groups, function (group) {
return _.map(group, function (item) {
return item[0];
}).join(" or ") + " [x]";
});
console.log(strings); The approach seems just fine to me.
However, I noticed that your fieldnames variable isn't actually used for anything. So that can go.
You can also use some shortcuts in underscore.js:
var groups, strings; | {
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Areas A math professor in an unheated room is cold and calculating. File:Moment of inertia rod center. Putting into layman's terms moment of inertia and how it relates to crankshaft rotation in a race engine - Circle Track Magazine. Science · Physics · Torque and angular momentum · Torque, moments, and angular momentum Rotational inertia Learn how the distribution of mass can affect the difficulty of causing angular acceleration. unit of moment of inertia is kg m² and C. Rotate both rods about their long axes (see Figure 2), in order to (continued) compare the moments of inertia of these rods about this axis. 1 Thin rod or bar, rotating about the centre. 0 m) and mass (M = 1. Area Moment of Inertia Section Properties of Solid Round Feature Calculator and Equations. Jul 12, 2017 · Lets first calculate the moment of inertia of the system about an axis passing through the common-point of one of the rods and perpendicular to the plane of the L. Let us take such a rod, of length 2x(figure), | {
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"url": "http://vkxt.mass-update.de/moment-of-inertia-rod.html"
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ros, moveit, ros-indigo, update
Anything I can do?
You could track down when and where this happens and file an issue on the github project.
That would (hopefully) help a lot.
--- EDIT ---
By now, this should be fixed upstream. See https://github.com/ros-planning/moveit/pull/589 .
Originally posted by v4hn with karma: 2950 on 2017-07-13
This answer was ACCEPTED on the original site
Post score: 2 | {
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fluid-dynamics, pressure, centrifugal-force, bernoulli-equation
If you were pressurizing a pipe, you can turn off the pump and just keep the system sealed and it can maintain pressure.
Another big one is losses. If you're pumping the fluid at high velocity you increase the viscous effects which would disapate energy much more than pumping at high pressure and low velocity (as far as I'm aware). | {
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astronomy, telescopes, cherenkov-radiation
The particle and anti-particle which are created are still very high energy - they have velocities near the speed of light in a vacuum. Whenever a particle flies through a substance at a velocity higher than the speed of light in that substance, it emits Cherenkov radiation. The typical analogy given is that this is like a sonic boom: in a sonic boom, distinctive waves are produced when something flies through a substance at higher than the speed of sound in that substance; with Cherenkov radiation, the waves are produced by flying through at more than the speed of light.
The particle and antiparticle might collide with stuff in the atmosphere, producing high-energy photons; these high-energy photons can pair-produce again. This way, the Cherenkov radiation amplifies; a small burst of Cherenkov light is produced whenever a gamma ray enters the atmosphere. | {
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php, pdo, session
I want to know if the way i did is correct, and if there's a safer way to do this
You need to ask how secure $_SESSION['email'] is. Could that value be updated, perhaps by a user profile update page?
Would it be simpler to use an attribute that would perhaps be stored in a relational table, to allow multiple users to be denoted as an admin?
Other review points
Use consistent indentation for the sake of readability maybe it was consistent before pasting in here but the block below has inconsistent indentation:
if( $_SESSION['logged_in'] != 1 || $_SESSION['email'] != 'admin17598@outlook.com'){
$_SESSION['message'] = "Algo deu errado :/";
header("location: ../error.php");
exit;
}else {
$username = $_SESSION['username'];
} | {
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beginner, c, programming-challenge
int alpha_convert(char *c) {
for (int i = 0; i < BOARD_LENGTH; i++) {
if (*c == cols[i]) {
return rows[i];
}
}
}
This is not necessary in C, because char and int are kind of the same thing. You can do regular calculations with characters just like you do with integers. Once in character, stay in character.
So when it comes to playing the game of converting between both types, I'd have to say the only winning move is not to play.
the mysterious void add_moves()
I have no idea what this function does.
void add_moves(int c, int n1, int n2) {
if (c >= 1 && c <= 8) {
if (n1 >= 1) {
moves[move_iter++] = num_convert(&c);
moves[move_iter++] = n1 + '0';
moves[move_iter++] = ' ';
}
if (n2 <= 8) {
moves[move_iter++] = num_convert(&c);
moves[move_iter++] = n2 + '0';
moves[move_iter++] = ' ';
}
}
} | {
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robot-localization, gps, nav2, navsat-transform-node, ekf-localization-node
<!-- output -->
<publish_odom>true</publish_odom>
<publish_odom_tf>true</publish_odom_tf>
<publish_wheel_tf>true</publish_wheel_tf>
<publish_distance>true</publish_distance>
<odometry_frame>odom</odometry_frame>
<robot_base_frame>base_footprint</robot_base_frame>
</plugin>
</gazebo> | {
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} |
thermodynamics, terminology
We sometimes have the courage of our convictions and use $\tau$ directly, which measures this thermodynamic temperature with units of energy, since $\sigma$ is a pure number and the derivative adds units of inverse-energy which we invert again. More often we try to approximate our liquid-thermometer scales by defining $T = \tau/k_\text B$ for some constant $k_\text B,$ dividing this energy into chunks called "kelvins" so that there are 100 chunks between the boiling and freezing points of water at atmospheric pressure, because that's what the Celsius scale used for its degrees. We then find that this requires the freezing point of water be at 273.15 kelvin, connecting the two scales completely. To help our equations we also usually define the "entropy" $S = k_\text B~\sigma.$ | {
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"url": null
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javascript, node.js, websocket, socket.io
var httpsServer = https.createServer(credentials, app);
var io = require('socket.io')(httpsServer);
var operationSocket = io.of("/operations")
// expressWs(app, httpsServer);
var con = mysql.createConnection({
host: process.env.DB_HOST,
user: process.env.DB_USER,
password: process.env.DB_PASS,
database: process.env.DB_NAME
});
var hostDetails = {};
function createExecOptions(host, container) {
return {
method: 'POST',
host: hostDetails[host].hostWithOutProtoOrPort,
port: hostDetails[host].port,
path: '/1.0/containers/' + container + '/exec',
cert: fs.readFileSync(hostDetails[host].cert),
key: fs.readFileSync(hostDetails[host].key),
rejectUnauthorized: false
}
}
const lxdExecBody = JSON.stringify({
"command": ["bash"],
"environment": {
"HOME": "/root",
"TERM": "xterm",
"USER": "root"
},
"wait-for-websocket": true,
"interactive": true,
}) | {
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# The relationship between the range and basis of a subspace
I'm fuzzy about the relationship of range and the basis of a subspace:
From book, I understand that:
Range is the set of all images of vectors of domain under T. Basis are set of vectors that span the subspace and are also linearly independent.
It seems like as if the basis could be the range(T). Can anyone clarify on that?
A basis of a vector space $V$ is a collection of vectors which are linearly independent and have span $V$.
The range of a linear transformation $T : V \to W$ is $R(T) = \{T(v) \mid v \in V\}$.
The two concepts, basis and range, are referring to features of different objects, as I have highlighted. Furthermore, a basis is a finite set of vectors, whereas the range of a linear transformation is a subspace which is only finite if it is $\{0\}$.
Example 1: Consider the vector space $\mathbb{R}^3$. A basis for $\mathbb{R}^3$ is $\{(1, 0, 0), (2, 3, 0), (4, 5, 6)\}$. | {
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javascript, jquery, beginner, object-oriented, html
// Toggle slide on the additional message focus / blur of corresponding input.
$("#signup input").on("focus blur", function(e) {
if (!$(this).siblings("#signup div").children("#signup .addition").hasClass("error")) {
$(this).siblings("#signup div").stop()[e.type === "focus" ? "slideDown" : "slideUp"]("fast");
}
});
$("#signup").on("submit", function() {
// Select first empty input if any, and don't submit.
$("#signup input").each(function() {
if ($(this).attr("type") !== "password") {
if (!$.trim($(this).val())) {
$(this).select();
return false;
}
} else {
// Password can contain spaces so no usage of trim for that.
if (!$(this).val()) {
$(this).select();
return false;
}
}
}); | {
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ros, navigation, odometry, rospy
Title: How to read msg from /odom at time series n and (n-1)
Hi there, I hope to compare the message from the consecutive time series n and (n-1) from /odom in python. I am confused about how to store the msg at time n-1 and time n at the same time, especially for the time sequence t=1.
def listener():
rospy.init_node('listener', anonymous=True)
rospy.Subscriber("/odom", Odometry, simple_callback)
rospy.spin()
def simple_callback():
if __name__== '__main__':
listener()
The problem which confused me is that: I was thinking to use some variables to store the msg at sequence n-1 and n like : current_odom=[ ] and last_odom=[ ]. However, I don't how to store the msg at time t=1, because listener() and simple_callback are in loop, I don't know when to pass the data in current_odom=[ ] and last_odom=[ ]. Could you please give me any hints?
Thank you. | {
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navigation, laserscan, costmap-2d, pointcloud
Originally posted by eitan with karma: 2743 on 2011-05-27
This answer was ACCEPTED on the original site
Post score: 2
Original comments
Comment by eitan on 2011-05-31:
Yes, slowing down the speed at which the laser tilts should give you a denser aggregated scan. There will, of course, be other trade offs with this, like the time it takes to see an obstacle of a certain height with the laser.
Comment by TayXR on 2011-05-29:
I am using hokuyo utm-30lx as my laser sensor. May I know what can i do to increase the density of my laser scan. Does slowing down the tilting speed of the laser sensor helps to increase it?
Comment by TayXR on 2011-05-29:
Hi eitan,
thanks for replying to my question. I was using voxel map_type previously which caused this problem. When I changed it to the costmap map_type, all the markings were able to be cleared without leaving any traces. So its might be what u had said, that my scan was not dense enough to see through the 3D cells. | {
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Situation
Given the parabola 3x2 + 40y – 4800 = 0.
Part 1: What is the area bounded by the parabola and the X-axis?
A. 6 200 unit2
B. 8 300 unit2
C. 5 600 unit2
D. 6 400 unit2
Part 2: What is the moment of inertia, about the X-axis, of the area bounded by the parabola and the X-axis?
A. 15 045 000 unit4
B. 18 362 000 unit4
C. 11 100 000 unit4
D. 21 065 000 unit4
Part 3: What is the radius of gyration, about the X-axis, of the area bounded by the parabola and the X-axis?
A. 57.4 units
B. 63.5 units
C. 47.5 units
D. 75.6 units
821 Rectangle minus semi-circle | Moment of Inertia Jhun Vert Mon, 04/20/2020 - 12:07 am
Problem 821
Find the moment of inertia about the indicated x-axis for the shaded area shown in Fig. P-821.
820 Unsymmetrical I-section | Moment of Inertia Jhun Vert Mon, 04/20/2020 - 12:05 am
Problem 820
Determine the moment of inertia of the area shown in Fig. P-819 with respect to its centroidal axes. | {
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java, asynchronous, error-handling, http
Now my theoretical ShardMappings class looks like this:
public class ShardMappings {
public Map<String, List<String>> primaryHostIdToPartitionMapping;
public Map<String, List<String>> secondaryHostIdToPartitionMapping;
public Map<String, List<String>> hostIdToMachineMapping;
public String getLocalPrimaryHostname(final String localDataCenterPath, final int shardId) {
final String localPrimaryHostId = primaryHostIdToPartitionMapping.get(localDataCenterPath).get(shardId);
final String localPrimaryHostname = getHostname(localDataCenterPath, localPrimaryHostId);
return localPrimaryHostname;
} | {
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galaxies
to a scaled up Milky Way than to a local ULIRG, such as Arp 220. A slightly older paper, Different Star Formation Laws for Disks Versus Starbursts at Low and High Redshifts, by some of the same authors, makes similar conclusions, on the basis of molecular gas observations. | {
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newtonian-mechanics, newtonian-gravity, drag, inertia
Title: Would a spinning object like a fan stop faster in a non-gravity environment? Let's say there is a fan spinning and stops in exactly 1 minute on earth. Would it stop faster or slower or exactly same time in a spacecraft without gravity but exact same density of air. Btw: let's assume friction on the axis is zero. Just trying to understand if gravity has any effect of stopping a symmetrically spinning object like a perfect wheel or fan.
EDIT:
Because air is complicating things let's just assume we test this experiment in vacuum, on earth and in space. No air involved. Friction on axis is neglected.
EDIT2:
Why would it stop without any air and axis friction? That's right. Let's put air back in. Without the air the question doesn't make any sense. Let's make your fan really big - say, as big as the moon.
You probably know the rotation of the moon is tidally locked to the earth - that is why we always see the same "face" of the moon. | {
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@ geeksforgeeks.org to report any issue with the above content obtained 0 at th! Find out the square root of 121 using repeated subtraction even number is odd expression. Find square root of a number ends in an odd number is multiplied by itself gives the number a! Of repeated subtraction, repetitive subtraction of odd numbers starting from 1, find whether given... Starting from 1, find whether the following numbers are perfect squares or not have subtract odd numbers starting 1... Itself is said to be followed while calculating the square root of a square. Be multiplied ( or ) divided so that the sum of the given.! Using this property to find the square root of 2, then it is to. We have to find the square of 100 first how can one become good at Data structures Algorithms... Squaring a number ] 99 – … repeated subtraction learnt the square of... Root number set of real numbers subtract odd numbers from the given number doubts, problems we... That of an even number is a perfect square | {
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homework-and-exercises, newtonian-mechanics, newtonian-gravity, orbital-motion, estimation
Oh - and there's one more thing: the tensile force at the back of the spear will be half the total force (1.5 GN), and with a surface area of $\mathrm{7 cm^2}$ that's a stress of 200 GPa. The ultimate strength of tungsten is about 1.5 GPa source, so it will rip.
I conclude that this feat is physically impossible - there is no spear that could withstand being thrown like this. | {
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algorithms, artificial-intelligence, computer-games
It's very easy to create a whole lot of different configurations for AIs.
It is possible to use with Genetic Algorithms: Each scorer has an associated weight, the weight can become the gene.
Using some tools, it is possible to check why a specific move was made and which scorers were mainly responsible for that move
Using tools, it is possible to create a map of the overall score/rank of possible moves (like the screenshot above)
By applying scores to the way the human plays, it is possible to create an "#AI_Mirror" which tries to make moves that it thinks the human would make
Disadvantages
It can be extremely difficult to adjust a score configuration "correctly", to make the AI play as good as possible.
Questions
Is the system I have built here widely known in the AI world? What would it be called in real AI terms?
Does this approach make sense or is there a different approach that you would recommend? | {
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electrostatics, electric-fields, work, potential-energy, gauss-law
$$
Now using Gauss law , $\rho = \epsilon_{0} \nabla\cdot\vec{E})$ and vector calculus identities we find that
$$
W = \frac{\epsilon_0}{2} \int_{\text{all space}} E^2 \, d\tau \tag{III}
$$
Now my doubt is this expression is always positive while the former expression (in case of discrete case) could take negative values as well. How this is possible even though continous case is considered as limit of finite cases? In equation (I) only the work spent to bring whole point charges (with finite charges) from infinity to the neighbourhood of each other is computed, but not the work spent to assemble each individual point charge, which is (theoretically) positive infinite for each point charge, because of the infinite repulsion overcome while compressing some finite amount of charge into a single geometric point. So the equation (II) and (III) count for that work and therefore they are positive. | {
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computational-chemistry
Further on, do I need to calculate the singlet state also with restricted open/unrestricted method?
It depends.
For most 'non-exotic' organic systems, there is no need to calculate the singlet state using an unrestricted method since, as you note, the results will often be indistinguishable. For systems with static correlation, though, if you still want to try to use a single-reference method, you will need to explore the unrestricted orbital space, as there may be a lower-energy solution where the alpha and beta orbital compositions appreciably differ. The primary method I'm aware of for such exploration is the "broken-symmetry" method. Two papers I know of that discuss the method, albeit not in extensive detail, are the following reviews by Frank Neese:
F. Neese. "Prediction of molecular properties and molecular spectroscopy with density functional theory: From fundamental theory to exchange-coupling." Coord Chem Rev 253: 526, 2009. doi:10.1016/j.ccr.2008.05.014 | {
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thermodynamics, energy, differential-equations, heat-conduction
Now, lets look at limit when time approaches infinity:
$$ \lim_{t \to \infty} \left(-T^{\prime} + \alpha \nabla ^{2}T\right) = -T^{\prime}$$
Thus first equation simply becomes
$$\frac {\partial T}{\partial t} = 0$$, at infinity time. This means that after long enough time there's no heat dissipation in material (no temperature change in material), because it has reached maximum heat capacity or maximum temperature in all body parts. Consider situation when you put cold metal in furnace, then heat starts to dissipate from one hot end to another cold end, until all metal rod becomes super-hot (all in red color). After this point metal rod isn't accepting anymore heat. At least there's no thermodynamic reason for a heat to travel in a rod from one end to another. | {
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ros
using namespace std;
void Request(const Test::Num& msg2)
{
Test::Num newMessage;
newMessage.data = msg2.data;
newMessage.header.stamp=ros::Time::now();
newMessage.header.frame_id="/current time"; */
ROS_INFO("I heard: [%s]", msg2.data);
}
int main(int argc, char **argv)
{
ros::init(argc, argv, "subscriber");
ros::NodeHandle m;
ros::Subscriber request_sub = m.subscribe("request", 1000, Request);
ros::spin();
return 0;
} | {
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python, path-planning, opencv, autonomous-car, dynamic-programming
My doubts/questions:
1) Am I implementing/proceeding rightly to help the car reach its destination? Are these ideas good or I should choose a different approach? If yes, please suggest.
2) How can I resolve the issue in my code? I don't know why I am getting this error. If I should use a different algorithm/approach, please sugget.
3) Is my adjacency matrix right? I made it based on 36 connecting nodes with weights.
I am not a computer science student but doing it because of my interest. I have got no guide/teacher to teach me these things and looking at this site to resolve my issues.
I request you to please provide guidance.
Thank you. I don't have time to do a full code review here, but the short version of why you're getting the error is that, as the error states, you're trying to remove an element from queue that either wasn't added or was already removed. | {
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| A lens I own (?)
#### Definition of a lens
##### Lenses
A lens is a custom view of the content in the repository. You can think of it as a fancy kind of list that will let you see content through the eyes of organizations and people you trust.
##### What is in a lens?
Lens makers point to materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.
##### Who can create a lens?
Any individual member, a community, or a respected organization.
##### What are tags?
Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.
| External bookmarks
#### Module to:
My Favorites (?)
'My Favorites' is a special kind of lens which you can use to bookmark modules and collections. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need an account to use 'My Favorites'. | {
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php
managerNegativeList = {addToSchedule,...};
adminNegativeList = { changeTitle,...}
if(isManager){
if(inMangerNegativeList){
die();
}
}
if(isAdmin){
if(inAdminNegativeList){
die();
}
}
processRequest(requestType,$requestData) | {
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convex-optimization, semidefinite-programming, polytope
For illustration, here is the set $T$: | {
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quantum-gate, qiskit, ibm-q-experience
Long explanation on the effects of barriers:
Barries have two related but relatively independent effects in two different stages: transpilation and scheduled execution.
Transpilation
As you mention, the transpiler does not optimize across barriers. Compare these two situations:
from qiskit import QuantumCircuit, transpile
circuit = QuantumCircuit(1)
circuit.h(0)
circuit.h(0)
display(circuit.draw())
display(transpile(circuit, optimization_level=2).draw())
If a barrier is set in the middle, the Hadamard gates wont be optimized:
circuit = QuantumCircuit(1)
circuit.h(0)
circuit.barrier(0)
circuit.h(0)
display(circuit.draw())
display(transpile(circuit, optimization_level=2).draw()) | {
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organic-chemistry, aromatic-compounds, reactivity, electrophilic-substitution, boron-family
Title: Electrophilic substitution on Borazole As Borazole ($\ce{B3N3H6}$) is aromatic, it can show electrophilic aromatic substitution. Now, my question is when borazole undergoes electrophilic aromatic substitution reaction, on which atom does the electrophile attack? Is it boron or nitrogen? Also, how to compare it's rate with the same type of reaction when carried on benzene? Should I consider stability of arenium ion (Wheland intermediate) formed when comparing the rates? Chiavarino, et al. [1] report that where electrophilic substitution occurs with carbocations (borazole more often undergoes addition), it does so on nitrogen. Nucleophiles such as methanol prefer boron. | {
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• To evaluate the pdf at multiple values, specify x using an array.
• To evaluate the pdfs of multiple distributions, specify a and b using arrays.
If one or more of the input arguments x, a, and b are arrays, then the array sizes must be the same. In this case, gampdf expands each scalar input into a constant array of the same size as the array inputs. Each element in y is the pdf value of the distribution specified by the corresponding elements in a and b, evaluated at the corresponding element in x.
Example: [1 1 2 2]
Data Types: single | double
Output Arguments
collapse all
pdf values evaluated at the values in x, returned as a scalar value or an array of scalar values. y is the same size as x, a, and b after any necessary scalar expansion. Each element in y is the pdf value of the distribution specified by the corresponding elements in a and b, evaluated at the corresponding element in x.
collapse all
Gamma pdf | {
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string-theory, lagrangian-formalism, variational-principle, boundary-conditions, action
Title: Using the open strings endpoints' boundary conditions and then obtain the EOM In Zweibach's A first course in string theory, he used the least action principle to get the equations of motion for strings, wehre the variation of action(which should be zero) is :
$$\delta S = \int_{\tau_i}^{\tau_f} d\tau [\delta X^\mu \mathcal{P}^\sigma_\mu]^{\sigma_1}_0 - \int_{\tau_i}^{\tau_f} d\tau \int_0^{\sigma_1} d\sigma \delta X^\mu \left(\dfrac{\partial \mathcal{P}^\tau_\mu}{\partial \tau}+ \dfrac{\partial \mathcal{P}^\sigma_\mu}{\partial \sigma} \right)$$
He then imposed the boundary conditions of the open strings endpoints (Dirichlet and Neumann) to let the first term vanish; and then he said that the second term must vanish as well. Doing so we got the equations of motion :
$$\dfrac{\partial \mathcal{P}^\tau_\mu}{\partial \tau}+ \dfrac{\partial \mathcal{P}^\sigma_\mu}{\partial \sigma} =0$$
Which are for both open and closed strings.
I have three questions: | {
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of the regular sieve.. For ranges with upper limit n so large that the sieving primes below √ n as required by the page segmented sieve of Eratosthenes cannot fit in memory, a slower but much more space-efficient sieve like the sieve of Sorenson can be used instead. Recommended: Please solve it on “ PRACTICE ” first, before moving on to the solution. As you may have realised, although the Sieve of Eratosthenes is usually described as an algorithm for identifying prime numbers it is actually the opposite. Sieve of Eratosthenes is a simple algorithm for finding all prime numbers up to any given natural number (in this dynamic worksheet, primes less than… Implement in a c program the following procedure to generate prime numbers from 1 to 100. We start with a large grid of whole numbers. Our website at the article might like to take a look at the article: Fill array. His only surviving work is Catasterisms, a book about constellations to the... A prime number using the approach described | {
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crucial to find the derivative of inverse functions. Evaluate these two partial derivatives at (1, 1 L) to get — respectively. We maintain a large amount of good reference materials on matters varying from multiplying polynomials to graphing linear. Here are some example problems about the product, fraction and chain rules for derivatives and implicit di er-entiation. Implicit di erentiation Statement Strategy for di erentiating implicitly Examples Table of Contents JJ II J I Page2of10 Back Print Version Home Page Method of implicit differentiation. Implicit Differentiation : Selected Problems 1. If a solution set is available, you may click on it at the far right. •!Students will be able to state Ohm’s law !=#$. Textbook solution for Calculus: Early Transcendentals 8th Edition James Stewart Chapter 3. The Derivative and the Tangent Line Problem b. Here is a set of practice problems to accompany the Implicit Differentiation section of the Derivatives chapter of the notes for Paul Dawkins | {
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fluid-dynamics, acoustics, temperature, frequency, viscosity
Edit 1: I used a tea kettle to heat the water and dropped it on a marble platform. I did the same experiment with cold (refrigerated) water using the same kettle. Height would be around 1.5m. There's a distinct difference between the sound produced.
Edit 2: I guess I won't need to do the experiment as @Deep suggested. Please view the link given by @Porges. Also, I was incorrect in relating the frequencies. Hot water makes higher frequency. Only thing is, how does bubbling make it more shrill? This is a guess since I have never done the experiment, but the viscosity of water falls by a factor of 5 on heating from 5°C to 100°C. The viscosity is one of the two factors (the other being density) that control the water flow, so it is quite reasonable to suppose that water at 100°C splashes in a noticably different way to water at 5°C. | {
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information-theory, randomness, data-compression, entropy
$$L_m(x) = a + b \left(\frac{x}{\sigma}\right)^2 + \log_2 \sigma$$
where:
$$a = \frac{\log_2 2\pi}{2} \approx 1.325$$
$$b = \frac{1}{2 \ln 2} \approx 0.721$$
This suggests that you should divide $x$ by $\sigma$, encode the remainder in $\log_2 \sigma$ bits, then encode the quotient $q$ in $a + bq^2$ bits (say, using arithmetic coding). Instead of storing $20002$ codes using Yuval's method, you now only need $20$ or so.
In a sense, what you're doing here is converting the normal distribution to a standard distribution. Moreover, if you move $\sigma$ to the nearest power of 2, the division can be done using bit shifts and masks. $\sigma=1024$ is close enough to $1000$, so that part of the operation is extremely cheap.
However, there is a catch. To arithmetic code $L_0(10)$, you need about 60 bits. On a 64-bit machine, this is pushing the practical limit of an efficient arithmetic coder. So you should probably consider partitioning the space for more efficient encoding. | {
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} |
• You're right, so what is the difference? I noticed using it the way I specified gave results identical to, say e.g. ListLogPlot when I use {#&, Log@# &} as the scaling. Sep 21, 2014 at 11:14
• @RunnyKine There are two issues here I think. First is that there are different forms for the option value: "{f,f^-1} use the scaling function f and its inverse f^-1" and "{s1, s2, ...} use several scaling functions si for direction i" so a direct substitution of ScalingFunctions -> scale in my code above will not work. The second issue is that even if I modify my Table iterator values to work with the shorter syntax the output still is not the same; the tick marks are different. I do not know why; I just assumed the "{f,f^-1}" format was needed internally. (continued) Sep 25, 2014 at 14:15 | {
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"lm_q2_score": 0.8688267762381844,
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"openwebmath_score": 0.33427321910858154,
"tags": null,
"url": "https://mathematica.stackexchange.com/questions/60272/how-do-i-change-axes-scale"
} |
strings, iteration, xslt
Title: Extracting the first two initials of a person's name I've come up with a hackish approach to get my XSL function to only return the first 2 initials of a person. I think there should be a more efficient way to do this though. The replace specifically is what I think I should be able to get rid of, looking through docs though I can't figure out how to correctly iterate with the split.
So 5 examples of my XML:
<name>
<surname>Test I</surname>
<given-names>Chris</given-names>
</name>
<name>
<surname>Test II</surname>
<given-names>Chris Chris</given-names>
</name>
<name>
<surname>Test III</surname>
<given-names>Chris Eat Meat</given-names>
</name>
<name>
<surname>Test IV</surname>
<given-names>Chris-Eat Meat</given-names>
</name>
<name>
<surname>Test V</surname>
<given-names>Chris-Eat-Meat</given-names>
</name>
My function call:
<xsl:value-of select="pull_it:get_initials(name/given-names/text())"/> <!-- name/given-names --> | {
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"tags": "strings, iteration, xslt",
"url": null
} |
# Finding x in an Olympiad simultaneous equation
I have been practicing for a an upcoming intermediate math olympiad and I came across the following question:
Let $x$ and $y$ be positive integers that satisfy the equations $$\begin{cases} xy = 2048 \\ \frac{x}{y}-\frac{y}{x}= 7.875.\end{cases}$$ Find x.
My approach
$$xy=2048$$
$$x=\frac{2048}{y}$$
$$\frac{\frac{2048}{y}}{y} - \frac{y}{\frac{2048}{y}} = 7.875$$
$$\frac{2048}{y^2} -\frac{y^2}{2048} = 7.875$$
$$2048^2 -y^4 =7.875\cdot 2048 y^2$$ If we compare the the first equation (x/y) - (y/x) = 7.875 to the euqtion that we just found ((sqrt. 2048)/y) - (y/(sqrt. 2048)) = 7.875 , x is in the same place so, x must be equal to the sqrt. of 2048.
Is this solution correct or are there any better solutions?
Thank you :) | {
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"url": "https://math.stackexchange.com/questions/1425006/finding-x-in-an-olympiad-simultaneous-equation/1425013"
} |
partial-order, data-flow-analysis, lattices, order-theory
I'm sure you can work it out. | {
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"tags": "partial-order, data-flow-analysis, lattices, order-theory",
"url": null
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newtonian-mechanics, classical-mechanics, rotational-dynamics, rotational-kinematics, oscillators
It is important to carefully consider the signs of variables when using graphical methods to obtain dynamical equations of motion, especially in phenomena involving rolling without slipping and the rigorous way to do this is to write all vectors as components of well defined unit vectors $\hat{i},\hat{j},\hat{k}$. Further, the relationship between variables and their signs depend on the choice of the coordinate system used, that is, the system comprised by $\hat{i},\hat{j},\hat{k}$. Overall, relying on writing scalar equations to execute dynamical analysis is a bad idea! | {
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"url": null
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$$\rm x\, =\, a\!+\!a^{-1}\Rightarrow\ x\,(x^2\!-3)\, =\, (a+ a^{-1})(a^2\! -1 + a^{-2})\, =\, a^3\!+ a^{-3}\! = 3 + 3^{-1}$$
Therefore $\rm\ \ 3x(x^2\!-3)\, =\, 3(3+3^{-1})\, =\, 10\ \ \$ QED
-
$x^2 - 3 = (a^2 + 2 + a^{-2}) - 3 = a^2 - 1 + a^{-2} \neq a^2 + 1 + a^{-1}$ – TMM Apr 13 '13 at 23:15
@TMM Yes, that's what was intended. Typos now fixed, thanks. – Math Gems Apr 13 '13 at 23:27
Another way: Since $x= 3^\frac{1}{3} + 3^\frac{-1}{3}$, $$\Rightarrow x - 3^\frac{-1}{3} = 3^\frac{1}{3}$$ Take cubes on both sides $$x^3 - \frac{1}{3} -3x.3^\frac{-1}{3}(x-3^\frac{-1}{3}) = 3$$
$$x^3 - \frac{1}{3} -3x.3^\frac{-1}{3}3^\frac{1}{3} = 3$$
$$x^3 - \frac{1}{3} -3x = 3$$ | {
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"tags": null,
"url": "http://math.stackexchange.com/questions/360087/x-sqrt33-frac1-sqrt33-what-is-3x3-9x/360089"
} |
beginner, go, roman-numerals
// Test samples
for _, sample := range samples {
result, err := IntToGlyph(sample.value)
if err != nil {
t.Errorf("Sample int %v should have produced glyph %v. Failed with %v", sample.value, sample.glyph, err)
} else if result != sample.glyph {
t.Errorf("Sample int %v should have produced glyph %v. Got %v", sample.value, sample.glyph, result)
}
}
// Test roundtrip conversion for numbers 1..2000
for i := 1; i <= 2000; i++ {
roman, err := IntToGlyph(i)
if err != nil {
t.Fatal(err)
}
backToI, err := GlyphToInt(roman)
if err != nil {
t.Fatal(err)
}
if i != backToI {
t.Errorf("Number %v failed roundtrip: %v > %v > %v", i, i, roman, backToI)
}
}
}
Test output:
ok roman 0.038s coverage: 100.0% of statements
Success: Tests passed.
Usage example (example/main.go file): | {
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Again, thanks a lot for any help! (Hints would be appreciated, I'll really try to understand the hints!) | {
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"url": "http://math.stackexchange.com/questions/356645/i-need-to-find-all-functions-f-mathbb-r-rightarrow-mathbb-r-which-are-conti"
} |
uniprot, interactions
Title: How to get all chemical compounds that interact with a given protein target? I want to get all Pubchem Chemical compounds (CID) that interact with a given UniProt target. I have a list of UniProt targets and I need to study the relationship between these targets and chemical compounds.
Thanks The easiest solution to the problem of mapping chemical compounds to protein IDs is to use the ChEMBL compound ID to UniProt mapping.
Doing this with PubChem is not so straight forward in part because its downloadable data format is a hideous obfuscated and badly documented mess split over multiple compressed files which in turn contain multiple compressed files...... For a publicly funded project they should really do better. | {
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"tags": "uniprot, interactions",
"url": null
} |
So far, you have discovered that
$$C4 = E5 = 5$$ and either $$A3$$ or $$B2$$ is $$5$$ with the other being $$3,5$$ or $$7$$. For now, Let us consider these as three separate cases.
Case 1
One of $$A3, B2$$ is $$7$$ and the other is $$5$$.
Since $$7 \times 5$$ is $$35$$, we see that this multiplication carries over $$3$$ to the next decimal place. This makes $$C3$$ equal to the last digit of $$A2 \times B2 + 3$$. The only possibilities therefore are
(i) $$A2 = B2 = 7$$ and $$C3 = 2$$.
(ii) $$A2 = 2$$, $$B2 = 5$$ and $$C3 = 3$$.
(iii) $$A2 = 2$$, $$B2 = 7$$ and $$C3 = 7$$. | {
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"openwebmath_score": 0.8825827836990356,
"tags": null,
"url": "https://puzzling.stackexchange.com/questions/106630/solving-kordemskys-prime-cryptarithm-and-proving-uniqueness"
} |
powershell, web-services, ip-address
If (Test-Path ([io.path]::Combine($rootPath, "$notoffice.txt")) {
Copy-Item ([io.path]::Combine($rootPath,"testy\hosts - $office")) $rootPath -Force
Remove-Item ([io.path]::Combine($rootPath,"$notoffice.txt")) -Force
New-Item ([io.path]::Combine($rootPath,"$office.txt")) -ItemType File -Force
}
While it might seem like I made it worse I have made it more robust and made future changes easier. Know that the use of [io.path]::Combine allow for making file paths easier without have to worry about placing slashes in between. I am more trying to draw attention to the use of the variable $rootPath.
Output from New-Item
The file object created by New-Item is going to be sent to output. Therefore you commonly see people suppressing that output for a cleaner program execution.
New-Item "C:\servertesting\$office.txt" -ItemType File -Force | Out-Null | {
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"url": null
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electromagnetism, general-relativity, black-holes, differential-geometry, vector-fields
\begin{equation}
A=\left(\frac{Q}{r_{+}}-\frac{Q}{r} \right)dt
\end{equation}
\begin{equation}
F=dA=\frac{Q^2}{r^2}dr \wedge dt
\end{equation}
where $r_{+}$ is the event horizon. Hence
\begin{equation}
F_{\mu \nu}F^{\mu \nu}=-2\frac{Q^2}{r^4}\,,
\end{equation}
which means the bulk integration on $\mathcal{M}$ just changes by a sign with respect to the magnetic solution. This is related to electromagnetic duality. However, in this case using the Stokes theorem leads to a non-zero boundary contribution, as it should, I think. Now my puzzle is why in one case we can use Stokes and the other it seems to fail. It turns out that in this case the vector field in which we apply Stokes is
\begin{equation}
v=\frac{Q}{r^2}\left(\frac{1}{r}-\frac{1}{r_{+}} \right) \frac{\partial}{\partial r}
\end{equation}
which seems to be smooth everywhere if we look at $g(v,v)$, using a good coordinate system. | {
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c++, object-oriented, game, sdl
return;
}
}
}
for (int enemyLaser = 0; enemyLaser < enemyLasers.size(); enemyLaser++)
{
if (findEnemyLaserCollisions(enemyLasers[enemyLaser], player))
{
printf("Player collision");
enemyLasers.erase(enemyLasers.begin() + enemyLaser);
return;
}
}
//No collisions detected
}
bool Game::findPlayerLaserCollision(Laser& playerLaser, Enemy& enemy)
{
//Player laser collisions
int playerLaserLeft = playerLaser.m_pos.x;
int playerLaserRight = playerLaser.m_pos.x + playerLaser.m_pos.w;
int playerLaserTop = playerLaser.m_pos.y;
int playerLaserBot = playerLaser.m_pos.y + playerLaser.m_pos.h;
//Enemy collisions
int enemyLeft = enemy.m_pos.x;
int enemyRight = enemy.m_pos.x + enemy.m_pos.w;
int enemyTop = enemy.m_pos.y;
int enemyBot = enemy.m_pos.y + enemy.m_pos.h; | {
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"tags": "c++, object-oriented, game, sdl",
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} |
php, mysql
</td>
</tr>
</table><br>";
}
echo"
<br><hr><br></div>";
}
if(mysql_num_rows($runsep) > 0 )
{ | {
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### Distribution Functions
Suppose that $$Z$$ has the standard normal distribution. Recall that $$Z$$ has probability density function $$\phi$$ and distribution function $$\Phi$$ given by \begin{align} \phi(z) & = \frac{1}{\sqrt{2 \pi}} e^{-z^2 / 2}, \quad z \in \R \\ \Phi(z) & = \int_{-\infty}^z \phi(x) \, dx = \int_{-\infty}^z \frac{1}{\sqrt{2 \pi}} e^{-x^2 / 2} \, dx, \quad z \in \R \end{align} The standard normal distribution is so important that $$\Phi$$ is considered a special function and can be computed using most mathematical and statistical software. If $$\mu \in \R$$ and $$\sigma \in (0, \infty)$$, then $$Y = \mu + \sigma Z$$ has the normal distribution with mean $$\mu$$ and standard deviation $$\sigma$$, and therefore $$X = |Y| = |\mu + \sigma Z|$$ has the folded normal distribution with parameters $$\mu$$ and $$\sigma$$. For the remainder of this discussion we assume that $$X$$ has this folded normal distribution. | {
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"url": "https://stats.libretexts.org/Bookshelves/Probability_Theory/Probability_Mathematical_Statistics_and_Stochastic_Processes_(Siegrist)/05%3A_Special_Distributions/5.13%3A_The_Folded_Normal_Distribution"
} |
optimization, c, performance
Note that it would be more normal to pass the start of the array and its size instead of the array plus two offsets.
functions could be static. This is of no significance in a one-file program but becomes important with bigger programs. Making functions and global variables static restricts their scope to the file which allows extra optimisation and reduces namespace pollution.
the output message needs a trailing \n
there is no prompt for the input values - ok that is trivial. Personally I find this sort of test better with values entered on the command line.
exit status is normally 1 (EXIT_FAILURE) on failure, not -1. On success it is 0 (EXIT_SUCCESS). These are UNIX conventions. | {
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} |
newtonian-mechanics, rotational-dynamics, rigid-body-dynamics
Also, we get $\dot{\mathbf r}_{\mathbf c}= \Omega l\cos(\theta)$, which is the same as Selene got , for a situation which is extremely similar. This made me believe that the approach is correct, but somehow in the end it gives a wrong answer ... Just what am I missing here? Is my definition not correct? You have missed a subtle but important fact, but it's alright since this is a very common mistake. Your equation is not wrong. The key point is that you forgot that the total angular velocity of the disk is not $\boldsymbol{\omega}$, but $\boldsymbol{\omega}+\boldsymbol{\Omega}$. In other words, relative to the lab frame, the disk is doing three things: | {
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rviz, rosbag, clock, tf2, rospy
But it should be something like:
[ INFO] [1473756806.521764836, 1473684710.202103154]: /level_laser_velodyne:
/ R R R 0 \
| R R R 0 |
| R R R 1.2 |
\ 0 0 0 1 /
Does anybody know what I am doing wrong?
Thank you for your help,
Tobias
Originally posted by Tobias Neumann on ROS Answers with karma: 179 on 2016-09-13
Post score: 2
It's not solved, but I've found a workaround by using a different node and therefore I'm closing this question.
I'm sorry that I can't help someone running into the same problem and ending up at this question.
Originally posted by Tobias Neumann with karma: 179 on 2018-11-07
This answer was ACCEPTED on the original site
Post score: 0 | {
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"tags": "rviz, rosbag, clock, tf2, rospy",
"url": null
} |
quantum-field-theory, vacuum, higgs
In quantum field theory the vacuum expectation value (also called condensate or simply VEV) of an operator is its average, expected value in the vacuum.
For all other particles the vacuum expectation value in the standard model is zero, for the Higgs it is 246GeV, at the broken state .
The conditions for symmetry existed at the beginning of the universe, according to the Big Bang model. The symmetry is broken at about 10^-10 seconds in the life of the universe (temperatures correspond to 100 GeV) and the Higgs field acquires the large vev. | {
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} |
algorithms, graphs, combinatorics
This function is computable, by enumerating all graphs with a certain number of vertices and edges. e.g., for each $n:=1,2,3,\dots$, for each $m:=0,1,2,\dots,n^2$, for each graph containing $n$ vertices and $m$ edges, test whether it is isomorphic to any you have computed before, and use that to enumerate the graphs. Of course, this will be a particularly inefficient algorithm.
In principle there is no known polynomial-time algorithm for computing graph isomorphism, so I would not expect a polynomial-time algorithm for $f$ (but this is not a proof; and it's still possible there might exist algorithms that are relatively efficient in practice). | {
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# Rotation Matrix of rotation around a point other than the origin
In homogeneous coordinates, a rotation matrix around the origin can be described as
$$R = \begin{bmatrix}\cos(\theta) & -\sin(\theta) & 0\\\sin(\theta) & \cos(\theta) & 0 \\ 0&0&1\end{bmatrix}$$
with the angle $$\theta$$ and the rotation being counter-clockwise.
A translation amongst $$x$$ and $$y$$ can be defined as:
$$T(x,y) = \begin{bmatrix}1&0&x\\ 0& 1&y\\0&0&1\end{bmatrix}$$
As I understand, the rotation matrix around an arbitrary point, can be expressed as moving the rotation point to the origin, rotating around the origin and moving back to the original position. The formula of this operations can be described in a simple multiplication of
$$T(x,y) * R * T(-x,-y) \qquad (I)$$
I find this to be counter-intuitive. In my understanding, it should be
$$T(-x,-y) * R * T(x,y) \qquad (II)$$
The two formulations are definitely not equal. The first equation yields | {
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postscript
This augments the function body with code which checks that there are indeed enough objects on the stack, or else it triggers a stackunderflow error. Then it checks that all of the arguments have the expected type, or else it triggers a typecheck error. The types here are written without the letters type at the end; these are added automatically.
You can omit the type name with the parenthesized syntax and it will allow any type for that argument. If you omit all the type names you still get the stackunderflow checking. With any of these errors the name of the user function is reported in the error message for easier debugging.
Implementation
Implementation-wise, the foundation is the pairs construct which is an array which gets traversed with forall. Any name beginning with @ gets the @ stripped off and the remainder gets executed. The results are enclosed in << and >> to create a dictionary. | {
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python, python-2.x, hash-map
It makes the dictionary definition to be the last segment of the code
which doesn't look neat.
The dictionary approach is recommended in Python as there's no switch statement in Python and it's better than a bunch of if-elif-else. You could also create the dict in a1.py based on the imported functions. Though I don't find its definition in a2.py okay.
Another option can be to fetch the functions from a2 module object itself if they can be re-named add, mul etc. This way you won't need a dict.
import a2
def arithmeticOps():
getattr(a2, 'add')(6, 1)
getattr(a2, 'mul')(6, 4) | {
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evolution, human-evolution
Title: How valid are Koestler’s criticism of evolutionary theory? I recently read Arthur Koestler's 1967 book The Ghost in the Machine. In it, Koestler criticises the neo-Darwinian theory of evolution—beneficial random mutations preserved by natural seleciton—as insufficient to explain the formation of complex forms like eyes and eggs. The issues Koestler has with the theory are ones that I've been trying to wrap my head around since before I read the book, but I'm aware that:
a) the book is half a century old;
b) Koestler was not a biologist or scientist; and
c) neo-Darwinian theory/the modern synthesis seems to have stood the test of time
so I'm wondering how accurate Koestler's account of the theory is, and if he is wrong what the retorts to his claims are. Here are two examples he gives of complex forms: | {
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javascript, html5, canvas, snake-game
element.requestFullscreen();
} else if(element.mozRequestFullScreen) {
element.mozRequestFullScreen();
} else if(element.webkitRequestFullscreen) {
element.webkitRequestFullscreen();
} else if(element.msRequestFullscreen) {
element.msRequestFullscreen();
}
}
window.onload = function(){
document.addEventListener("fullscreenchange", function(){snake.game.adjust();});
document.addEventListener("webkitfullscreenchange", function(){snake.game.adjust();});
document.addEventListener("mozfullscreenchange", function(){snake.game.adjust();});
document.addEventListener("MSFullscreenChange", function(){snake.game.adjust();}); | {
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"tags": "javascript, html5, canvas, snake-game",
"url": null
} |
algorithms, optimization, scheduling, integer-programming
Title: Interval scheduling problem with priorities I have a problem that is similar to the interval scheduling algorithm but it involves priorities. My data sets consist of the following data:
Cars with the start and end time of parking, along with their one or more attributes (e.g. electric vehicle, motorcycle, handicapped).
Parking spots along with zero or more attributes and lot number.
Attributes with their priorities. For example if the property handicapped is given a value of 1, cars that have that attribute should be assigned a parking spot first. Attributes are hard constraints, the priorities of the attributes determine the order of assignment. | {
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special-relativity, particle-physics, energy-conservation, mass-energy
Intuitively, the initial spatial-momentum of the system in the lab frame
comes from the moving antiproton since the target proton is at rest.
In my opinion, many problems in relativity are treated only as algebra problems.
However, when treated geometrically and trigonometrically [the reason for many of the algebraic invariants and formulas], there is something more tangible
and can be more easily interpreted physically. (With spacetime and vector methods, it is analogous to working with a free-body diagram for an object in equilibrium.) | {
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thermodynamics, quantum-field-theory, string-theory, quantum-gravity
in String Theory). I know for a fact that I will need things like EMF, relativity, quantum mechanics, QFT and so on but thermodynamics, as I already, is probably something I will forget about from the time I do it (second year BSc) all the way to the time I begin String Theory (PhD). Also, yes, my university does teach String Theory at PhD level and even offers it at an introductory level at MSc. This seems like a strange question, unless I've misunderstood, as you're asking more about university module advice as opposed to a more general question about thermodynamics & string theory (as the title implies)? It'd be helpful to know if you're asking whether you should pick it over a different module, or just whether you can not study very hard in it, or something different? | {
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c#, entity-framework
bSuccessful = TryDataBaseAction(dbEntities, out ErrorMessage,
() =>
{
dbEntities.Men.Add(new Man { ManID = M.ManID, Name = M.Name });
});
StatusMessage = AssignDBStatusMessage("Records created successfully", ErrorMessage, bSuccessful);
return bSuccessful;
}
public bool UpdateMan(TestDatabaseEntities dbEntities, IQueryable<Man> query, out string StatusMessage, Man man)
{
string ErrorMessage;
bool bSuccessful;
bSuccessful = TryDataBaseAction(dbEntities, out ErrorMessage,
() =>
{
foreach (Man M in query)
{
M.Name = man.Name;
}
});
StatusMessage = AssignDBStatusMessage("Records updated successfully", ErrorMessage, bSuccessful);
return bSuccessful;
} | {
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quantum-field-theory, heisenberg-uncertainty-principle, feynman-diagrams
Title: Feynman diagram and uncertainty I have been introduced to the Feynman diagrams in QFT after following Wick-Dyson tedious formalism.
Two things are unclear, though, about the Feynman shortcut to compute scattering amplitudes.
What are the horizontal and vertical axes in these diagrams? Are they $x$ and $t$ respectively or $x$ and $y$?
If yes then we are drawing a particle with an exact momentun $p$.
But doesn't this violate the uncertainty principle since we are assuming exactly measured $x$ and $p$? There are no axes in Feynman diagrams. The only important part of a diagram is what is connected to what, and not the relative orientation. You can move around the pieces of a diagram and, as long as you don't break any line, the value of the diagram remains unchanged. | {
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homework-and-exercises, electric-circuits
The magnitude of $U_a$ is the amplitude you will measure. The angle (phase) of $U_a$ is the phase you will measure.
UPDATE: In response to the last question: First, we limit $\omega$ to being a real number. Now, if you work out $\frac{U_a}{U_e}$ by hand (something I highly recommend if you haven't), you should get (assuming I've not made an error):
$\frac{U_a}{U_e} = \dfrac{j \omega RC}{1 - (\omega RC)^2 + j3 \omega RC}$
Now, you can "see" where this is maximum without calculation. As $\omega$ increases from zero, the real part of the denominator is decreasing and becomes zero when $\omega = \frac{1}{RC}$. From that point on, the magnitude of the denominator increases faster than the magnitude of the numerator. | {
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observational-astronomy, asteroids, astrometry
This excellent answer from @MikeG shows exactly how to find a list of observations for a minor planet. But I'd like to ask about a list of observations of an artificial object.
Currently the NASA JPL's Horizons site is also providing predicted trajectory of an unusual spacecraft which is referred to as Roadster. It is the cherry-red Tesla Roadster attached to a roughly 3.6 x 8 meter white rocket body in heliocentric orbit, and it has been tracked by many different observatories because of its unique circumstances. (some GIFs in this answer) Roadster's 4.6 minute rotational period was also recently reported.
Currently Horizons is reporting solution #7. They have been updating their solutions regularly as new observations are made and reported because as Roadster recedes from Earth it is rapidly dimming and will soon pass magnitude +20, so each new solution helps for the reacquisition of the object as it dims. | {
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black-hole, milky-way
Finally, as they merge, which, might take quite a bit of time if they end up orbiting each other, perhaps millions, even billions of years. If/when they do merge, there could be some curious and not very well understood gravitational wave effects. bending and stretching of space like ripples. (Gravity already bends space, but not in measurable ripples. Our observation's of gravity warped space is a smooth curve.
I'll re-post this article here from comments that says it's possible for 2 black holes to repel each other if they bend space in opposite spin-directions and approach each other on a level plane. Less close and they could still easily disrupt outer planet orbits, casting some planets every which way. | {
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c++
Notice that by having a few helper functions around, we were able to:
Get rid of duplicate code
Remove many unnecessary comments by giving functions good, descriptive names
Organize our code into logical units
Keep the main function clutter-free and allow the reader to have a better idea of the high-level logic of the program.
Get rid of all the global values and allow us to declare variables only when we needed to. | {
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